Area-efficient, width-adjustable signaling interface

ABSTRACT

A lateral transfer path within an adjustable-width signaling interface of an integrated circuit component is formed by a chain of logic segments that may be intercoupled in different groups to effect the lateral data transfer required in different interface width configurations, avoiding the need for a dedicated transfer path per width configuration and thereby substantially reducing number of interconnects (and thus the area) required to implement the lateral transfer structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/793,029, filed Oct. 25, 2017 (now U.S. Pat. No. 10,102,887), which isa continuation of U.S. patent application Ser. No. 13/315,149, filedDec. 8, 2011, which claims the benefit of U.S. Provisional ApplicationNo. 61/438,861, filed Feb. 2, 2011. Each of the above-identified patentapplications is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to the field of electroniccommunications and more particularly to signaling between integratedcircuit devices.

BACKGROUND

In an integrated circuit (IC) device having an adjustable-widthsignaling interface, a selectable number of input/output (I/O) pins maybe used to convey information-bearing signals, thus enabling an IC to beconfigured according to system requirements. In the context of a memorysystem, for example, a single memory IC having an adjustable width datainterface that ranges from N I/O pins to N/M (N divided by M) I/O pinscan be used to support the various pin widths demanded by differentindustry sectors, and can also be used to support capacity expansiontechniques in which the number of signaling links allocated to a givenmemory IC is diluted (or reduced) as the memory IC population isincreased.

Unfortunately, width adjustability has been limited to relatively lowmax/min width ratios (i.e., ratio of N to N/M, and thus low values of M)due to practical constraints involved with laterally transferring thedata along the interface between internal registers and the I/O pins.More specifically, each halving of the interface width typicallyrequires a lateral transfer bandwidth equal to the link bandwidthitself—a transfer bandwidth that begins to consume an impracticallylarge volume of interconnect resources as the max/min width ratio growslarger than two. Moreover, signal propagation delay associated with thetransfer tends to increase with the square of the physical transferdistance which itself is typically proportional to the max/min widthratio.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1A contrasts the lateral-transfer bandwidth requirement of alateral transfer structure formed by daisy-chained transfer segmentsaccording to one embodiment with the bandwidth required by multiplexinga set of discrete, continuous transfer paths;

FIG. 1B illustrates different signal flow paths formed within thesegmented lateral transfer structure of FIG. 1A for logicalinterface-width configurations ×8, ×4, ×2 and ×1;

FIG. 2 illustrates a memory IC signaling interface having a ×16 nativewidth in which each link transceiver performs a 1:16 write datadeserialization, thus delivering up to 256 bits of write data to thememory core per memory access;

FIGS. 3A-3E illustrate different interface widths that may be enabled byrespective combinations of composite paths within individual instancesof the W16 transfer blocks shown in FIG. 2;

FIG. 4 illustrates the signaling interface of FIG. 2, showing detailwithin exemplary read-data transfer blocks that form part of thelateral-transfer circuitry;

FIG. 5 illustrates an alternative layout of transfer cells within a W16transfer block that increases the die area available for transfer cellimplementation;

FIG. 6A illustrates an alternative lateral transfer structure thatenables the lateral transfer distance within the worst-case transferconfiguration to be cut approximately in half;

FIG. 6B illustrates embodiments of bidirectional transfer cells and thatmay be employed within a bidirectional lateral transfer structure toenable the interface width configurations shown in FIG. 6A;

FIG. 7 illustrates a further reduction in lateral transfer bandwidthenabled by the centered I/O approach described in reference to FIGS. 6Aand 6B;

FIG. 8 illustrates an embodiment of a ×16 signaling interface modifiedrelative to signaling interface of FIG. 2 to include split-route,bidirectional transfer cells corresponding to transfer cell 375 of FIG.7;

FIGS. 9A-9E illustrate exemplary interface widths enabled by thesplit-route, bilateral transfer blocks of FIG. 8, and the transfer-statecontrol signals applied to the transfer cells therein;

FIG. 10 illustrates an expanded view of an 8-I/O single-source clusterwithin the ×2 configuration shown in FIG. 9D;

FIG. 11 illustrates an alternative layout of transfer cells (W2) withina W8 transfer block that increases the die area available for transfercell implementation;

FIG. 12 illustrates an embodiment of a split-route, bidirectionaltransfer cell that may be used within the read data path of a ×16 ICsignaling interface;

FIGS. 13A-13E illustrate exemplary interface widths enabled by thesplit-route, bilateral transfer blocks of FIG. 12, and the state controlsignals applied to each of the transfer cells therein;

FIG. 14 illustrates an expanded view of an 8-I/O single-source clusterwithin the ×2 configuration shown in Figure; and

FIGS. 15A-15C illustrate embodiments of memory systems havingadjustable-width memory components that may employ any of the segmentedlateral transfer paths as described herein.

DETAILED DESCRIPTION

Integrated circuit devices having area-efficient, width-adjustablesignaling interfaces formed by segmented lateral transfer paths aredisclosed in various embodiments. In one embodiment, for example, alateral-transfer path is formed by daisy-chained segments that includelogic to select an input signal from either a downstream path segment ora local I/O node and transfer the selected input signal to both anupstream path segment and to a local destination register. By thisarrangement, different subsets of the daisy-chained segments may beapplied to effect lateral data transfer in different widthconfigurations, avoiding the need for a dedicated transfer path perwidth configuration and thereby substantially reducing number ofinterconnects (and thus the area) required to implement the lateraltransfer structure. In other embodiments, I/O nodes physically centeredbetween data destinations (and sources) are selected to be the activeI/O nodes in below-maximum width configurations thus halving(approximately) the lateral transfer distance and propagation time fromI/O node to data destination. In yet other embodiments, the dataincoming/outgoing via a given I/O node is split into upper and lowerportions, with the upper data portion being laterally transferredto/from logic-side data registers above the I/O node and the lower dataportion being laterally transferred to/from logic-side data registersbelow the I/O node. Because only half the total incoming data volume islaterally transferred in either direction, the net lateral transferbandwidth (and thus the number of interconnects and area consumedthereby) is halved relative to the transfer bandwidth otherwiserequired. These and other embodiments are disclosed in further detailbelow.

FIG. 1A contrasts the lateral-transfer bandwidth requirement of alateral transfer structure 111 formed by daisy-chained transfer segmentsaccording to one embodiment with the bandwidth required by multiplexinga set of discrete, continuous transfer paths (101).

In the continuous-path approach, shown at 101, the implementation arearequired by the conductors of the lateral-transfer structure (shaded) isdependent on the range of I/O widths supported by the signalinginterface, N_(max) to N_(min). That is, each halving of the interfacewidth (i.e., from N_(max) to N_(max)/2, from N_(max)/2 to N_(max)/4,etc.) necessitates an additional lateral transfer path having bandwidthBW_(Link) (i.e., as shown by paths marked “×4”, “×2” and “×1”), and thusan additional number ‘n’ of lateral-transfer conductors corresponding tothe serialization/deserialization ratio within the link transceivers(DQ) of the physical signaling interface (PHY). Assuming aserialization/deserialization ratio of 16, for example, the physicalwidth of lateral transfer structure 101 grows by 16 conductors for eachhalving of the logical interface width (i.e., physical width of thelateral transfer structure is proportional toLog₂(N_(max)/N_(min))*BW_(Link)), a growth that rapidly exceeds theavailable implementation area and thus constrains the supportablelogical interface widths to a relatively small range.

By contrast, the implementation area required by segmented lateraltransfer structure 111 is independent of the range of supportedinterface widths and instead defined by the conductor count needed tosupport the bandwidth of a single link. In effect, by decomposing thelateral transfer structure into daisy-chained segments that can beswitchably coupled to one another to form composite transfer paths ofdifferent lengths, and by limiting the PHY-side connection to a givencomposite transfer path to a solitary I/O node (i.e., the active I/Onode used to source data to the core-side registers coupled to thecomposite transfer path), the full range of logical interface widthselections, from the native or maximum width of the interface, Nmax, toa single I/O node (Nmin=1) may be achieved. Moreover, as discussed infurther detail below, the individual segments may include bufferamplifiers that limit the t_(RC) delay of laterally transferred signals,thus avoiding RC-dependent flight time delays that plague conventionalimplementations.

Still referring to FIG. 1A, which illustrates input data flow, segmentedlateral transfer 111 is formed by a daisy chained set of lateraltransfer segments (e.g., as shown at 121 a, 121 b, 121 c), that enableformation of one or more lateral transfer paths between I/O nodes in PHY110 and core registers within core 112. PHY 110 may form, for example,at least part of the physical signaling interface of memory IC 100,while core 112 represents the functional core of the IC (e.g., a memoryarray and circuitry to control access thereto in the case of memory IC100) and is generally represented herein as a set of input or outputregisters for receiving data from or delivering data to PHY 110 vialateral transfer structure 111.

Each lateral transfer segment 121 (e.g., 121 a, 121 b, 121 c) withinsegmented lateral transfer structure 111 is referred to herein as a“transfer cell” and is coupled to a local I/O node within PHY 110 (e.g.,a pin or other link-interconnect 117 and data transceiver 119), and to alocal core register 120, as well as to sets of one or more conductors126 u, 126 d that form respective segments of a segmented lateraltransfer path. Referring specifically to transfer cell 121 b, a pair ofswitching elements 123, 125 are provided to switchably couple either thelocal I/O node or input transfer path segment 126 d to output transferpath segment 126 u and to local core register 120 (collectively, the“cell output”), thus enabling either the local I/O node or thedownstream transfer cell to source data to the cell output. Moreover,input transfer path segment 126 d constitutes the output transfer pathsegment of downstream transfer cell 121 a, and output transfer pathsegment 126 u constitutes the input transfer path segment to upstreamcell 121 c, thus establishing a daisy-chain(input-to-output-to-input-to-output, . . . ) of transfer path segmentsthat can be driven by any of the data I/O nodes within the interface.More specifically, the “I/O” switching elements 123 within the chain oftransfer cells may be configured to establish a single I/O node source(the active I/O node) within a cluster of I/O nodes, and the “transfer”switching elements 125 may be configured to establish one or morecomposite transfer paths, each switchably isolated (i.e., decoupled)from one another to conduct input data from the active I/O node to thesubset of the core registers corresponding to the I/O node cluster.

FIG. 1B illustrates different signal flow paths formed within thesegmented lateral transfer structure 111 of FIG. 1A for logicalinterface-width configurations ×8, ×4, ×2 and ×1 (i.e., 8 active I/Onodes, 4 active I/O nodes, 2 active I/O nodes and a single active I/Onode). Active I/O nodes and inactive I/O nodes are distinguished byfilled (solid black) and unfilled interconnects 117, respectively, andactive and inactive signal paths (i.e., used and unused signal paths)are similarly shown by heavy (bold) and light (non-bold) line weights,conventions that are employed throughout the drawing figures. As shown,in a maximum or native-width interface configuration (i.e., ×8 in theparticular example depicted), all transfer switching elements are openedand all I/O switching elements are closed to establish a respectivedirect path (i.e., no lateral transfer) from each I/O node to thecorresponding core register (i.e., exclusively from local I/O node tolocal core register). By contrast, in the ×4 interface, each transfercell in the chain is alternately configured to select thelateral-transfer input (transfer switching element closed, I/O switchingelement open) or the local I/O node as the input data source, therebyestablishing four active I/O nodes each of which sources data to acluster of two core interface registers through a respective one of fourdistinct composite transfer paths 151. In the ×2 configuration, thetransfer cells are configured to establish two active I/O nodes, each ofwhich sources data to a respective half of the core interface registers(clusters of four interface registers) via a composite transfer path 153that extends from the transfer cell for the active I/O node through thetransfer switching elements for three upstream transfer cells. In the ×1configuration, the transfer cells are configured to establish a singleactive I/O node (i.e., all I/O switching elements opened) that sourcesdata to the full set of core I/O registers via a composite transfer path155 that extends through all the transfer cells (i.e., all transferswitching elements closed).

Comparing the different interface-width configurations shown in FIG. 1B,it can be seen that a composite transfer path applied in a given logicalinterface width is split into two distinct transfer paths when theinterface width is doubled. Said another way, any two composite transferpaths applied in a given logical interface width are switchably coupledand thereby re-used to form a yet larger composite path when theinterface width is halved. Thus, instead of requiring a new dedicatedtransfer path for each halving of the logical interface width, thedaisy-chained segmented transfer path enables path segments to bere-used in each configuration, thereby avoiding the need for extrasignal conductors to accommodate different logical interface widths (andthe resulting range-dependent area consumption) that plaguesconventional adjustable-width signaling interfaces.

Returning to FIG. 1A, because each transfer cell 121 a, 121 b, 121 cselects either the local I/O node or the lateral-transfer input (i.e.,from the downstream cell) to drive the cell output, the I/O and transferswitching elements are always in opposite states and thus constitute atwo-state multiplexer (e.g., as shown at 131 within transfer cellembodiment 130). More generally, the transfer cell itself may be viewedas having one of two states: an I/O state to select the local I/O nodeas the input data source, or a transfer state that enables lateral(cell-to-cell) signal transfer. Thus, in the ×1 configuration shown inFIG. 1A (and at the far right in FIG. 1B), all transfer cells are in thetransfer state (note that, though not shown or required, a transfer cellmay also be provided in association with the bottom “always-active” I/Onode, for example, to establish propagation time symmetry), while in the×8 configuration shown in FIG. 1B, all transfer cells are in the I/Ostate. In each of the intermediate width configurations (i.e., less thanthe native or maximum width and greater than ×1 width), the transfercells are mixed between transfer and I/O states, with the number ofI/O-state transfer cells being equal to the logical interface width andthe remaining transfer cells being in the transfer state to establishone or more composite transfer paths.

Different embodiments of two-state transfer cells that may be used toimplement transfer cells 121 are shown at 130 and 140. In transfer cell130, pass gates 133 and 135 (i.e., parallel N-type and P-type transistorelements coupled in parallel) are used to implement I/O and transferswitching elements 123 and 125, respectively. Complementary instances ofselect signal, ‘S,’ (generated in part by inverter 137) are supplied tocontrol (gate) terminals of pass gates 133, 135 such that one of thepass gates is closed when the other is open and vice-versa, thusestablishing a two-input multiplexer 131. In alternative embodiments,the I/O and transfer switching elements 123, 125 may be implemented byvarious circuit elements other than the pass-gates shown, includingBoolean logic implementations in which the multiplexer select signal, S,I/O data input (W_(I)) and transfer data input (Y_(I)) are logicallymultiplexed to yield output signal Y_(O)/W_(O).

While transfer cell 130 may suffice for relatively small interfacewidths, signal attenuation and t_(RC) delay tend to increase rapidly asthe cell count grows. To overcome these difficulties, transfer cell 140includes, in addition to elements 133, 135, 137, a transfer buffer 145(e.g., implemented by back-to-back inverter stages and optionallyforming part of multiplexer 141) to drive the transfer output, Y_(O),and an isolation buffer 147 to isolate the transfer output from thelocal output, W_(O) (i.e., output coupled to the local core register),thereby providing a signal repeater at each transfer stage that maysubstantially lower the overall propagation time of a laterallytransferred signal from the source I/O node to the most remotedestination register. That is, in contrast to a continuous path approachin which the propagation delay grows in proportion to the square of thetransfer path length (i.e., due to linearly increasing resistance andlinearly increasing capacitance, and thus quadratically increasingt_(RC)), cell-by-cell buffering of transfer path segments limits thet_(RC) delay along any given transfer path segment to yield apotentially lower net propagation delay along the segmented lateraltransfer path than may be achieved using a continuous path approach.

Still referring to FIG. 1A, segmented lateral transfer structure 111 andsegmented lateral transfer structures according to other embodimentsdiscussed below may be deployed within the data interface ofintegrated-circuit memory device 100 (a “memory IC” such as a DRAM,SRAM, flash memory IC or any other IC having a mass storage array thatconsumes a substantial or predominant portion of the IC die area) toenable logical width adjustment ranging from the native or physicalwidth of the data interface (Nmax) to a predetermined minimum logicalwidth (Nmin). More generally, while many of the embodiments herein arediscussed in the context of a memory IC and the flow of incoming writedata and outgoing read data, the lateral transfer techniques andcircuitry disclosed may in all cases be used to effect lateral transferof other signal types within memory ICs, memory controllers or any othertype of integrated circuit component. Also, while signaling interfacesare generally depicted as having native widths of ×8 or ×16 and minimumlogical widths of ×1, wider or narrower native widths and/or largerminimum logical widths may apply. Similarly, while the interface widthsshown in FIG. 1B and other embodiments are progressively halved toestablish each narrower width configuration (i.e., N_(max)*2⁻¹, where iranges from 0 to log₂ Nmax), the available width configurations are notlimited to those depicted and may include intermediate widths that arenot factor-of-two multiples (or fractions) of other logical widths.

FIG. 2 illustrates an exemplary memory IC signaling interface 175 havinga ×16 native width in which each link transceiver (DQ 190) performs a1:16 write data deserialization, thus delivering up to 256 bits of writedata to the memory core per memory access. As shown in detail view 176,each link transceiver 190 includes a signal receiver 193 and outputdriver 203 that are enabled during memory write and memory readoperations, respectively (i.e., by enable logic gates 194, 204 that arecontrolled, at least in part, by enable-write (EnW) and enable-read(EnR) signals). The signal receiver 193 forwards a serialized write datasignal (received via an external signaling link coupled to interconnectnode 117) to 1:16 deserializing circuit 195. When enabled by logic 206,deserializing circuit 195 parallelizes successive bits of the incomingserial data signal in response to rising and falling edges of adata-rate clock signal, MCK4 (shown to be 1.6 GHz in this example andothers below, though higher or lower frequency clock signals may be usedin all cases), to yield a sequence of 16-bit write data values that areclocked into a 16-bit write data register in response to respectiverising edges of a core clock signal, MCK1 (shown to be 0.2 GHz in thisexample and others below, though higher or lower frequency clock signalsmay be used), thereby forming respective write data words,Wdata[i][15:0], where ‘i’ is the link index. The read data output pathwithin link transceiver 190 is essentially the reverse of the write datainput path with each 16-bit read data word resulting from a memory readaccess (Rdata[i][15:0]) being clocked into read data register 209,serialized into a serial bit stream within serializer 205 and thendriven onto signaling link ‘i’ (i.e., the external link coupled tointerconnect 117) by output driver 203. Like the signal receiver anddeserializer in the write data path, serializer 205 and output driver203 may be selectively enabled (e.g., turned on only during read datatransmission) by logic circuitry 206 and 204, respectively.

Focusing on the write data path, the sixteen write data values,Wdata[i][15:0] (where i ranges from 15 to 0 in the example shown), aredelivered to respective write-data transfer blocks, “W16,” that,together with counterpart read-data transfer blocks, “R16,” constitutethe lateral transfer circuitry within the signaling interface. In oneembodiment, shown in detail view 177, each W16 block may be viewed as anarray of interconnect cells, that include bit-transfer cells, W1 (179),and bit-routing cells, W0 (181). In the particular example shown,transfer cells 179 are disposed in a diagonal within the interconnectcell array (i.e., at array positions [i, i], where ‘i’ ranges from 0 to15, and where array position [0,0] is situated at the bottom left cornerof the array) so that the input and output signals for each transfercell 179 may be conveyed exclusively through routing cells 181 as theyextend to/from edges of the W16 block. As shown, each W1 cell includes amultiplexer 185 (which may internally include a buffer amplifier asshown at 141 in FIG. 1A) that selects between a local write-data inputbit (W_(I)) and a lateral transfer input bit (Y_(I)) and drives theselected data bit (selected by a select signal, S[i], that is applied incommon to all transfer cells 179 within block W16[i]) to the lateraltransfer output (Y_(O)) and, via isolation buffer 186, to the localwrite-data output (W_(O)). As shown, the write-data outputs, W_(O)[15:0]are routed to respective destination data registers 212 within the core.

FIGS. 3A-3E illustrate different interface widths that may be enabled byrespective combinations of composite paths within instances of the W16transfer blocks shown in FIG. 2 (each of which may be viewed as a 16-bitwide instance of the write data transfer cell W1). As shown in FIG. 3A,when the individual select signals, S[i], of select value S[15:0] areall ‘1’ (i.e., a logic high state, though the inverse logic state couldalternatively be used), the 16-bit write data value from each local DQis delivered directly via the corresponding (local) W16 block to thecorresponding (local) core register, thus effecting a 16-bit wideinterface in which 256 bits of data are delivered to the IC core at apeak rate corresponding to the MCK1 frequency. No lateral transfer iseffected.

In the ×8 interface (FIG. 3B), every other select signal (i.e., the oddvalued select signals, S[1], S[3], . . . , S[15] are set to a logic ‘0’state, thus rendering half the I/O nodes (DQ[1], DQ[3], DQ[15]) inactiveand establishing eight composite lateral transfer paths to deliver writedata to the core registers corresponding to the inactive I/O nodes.

In the ×4 interface of FIG. 3C, three out of every four select signalsare set to a logic ‘0’ (with only select signals S[j*4], where T=0, 1,2, 3, being raised). In the ×2 interface (FIG. 3D), only select signalsS[j*8] (where T=0,1) are raised, and in the ×1 interface (FIG. 3E), onlyselect signal S[0] is raised.

FIG. 4 illustrates the signaling interface 175 shown in FIG. 2, showingdetail within exemplary read-data transfer blocks (“R16” blocks) thatform part of the lateral-transfer circuitry. In the embodiment shown indetail view 215, each R16 block is implemented in generally the samemanner as the W16 block shown in FIG. 2, but re-oriented (i.e., flippedabout the X axis and the Y axis) to establish memory core registers 214as the data source and the DQ-side read data register 209 as the memorydestination. Referring to detail views 217 and 219, for example, routingcell R0 is identical to routing cell W0 (with signal names changed toreflect direction and data source), and transfer cell R1 is implementedin essentially the same manner as cell W1 (having a multiplexer 221 andisolation buffer 223), except for reversal of inputs and outputs.

FIG. 5 illustrates an alternative layout of transfer (W1) cells within aW16 block 230 that increases the die area available for transfer cellimplementation. That is, viewing the sixteen W1 cells as a 4×4 cellarray that is to be distributed within the 16×16 W16 block in a mannermaximizes (or at least increases) the distance between neighboringcells, then each W1 cell may be disposed four array positions (i.e.,dimension of axis, 16, divided by number of W1 cells to be disposedalong that axis, 4) from its neighbor in an adjacent row or column. TheY_(I)/Y_(O) signal groups are remapped accordingly as shown by thesignal group numbering along the upper and lower edges of W16 block 230.By this arrangement, the die area available for implementation of themultiplexing element and isolation amplifier is expanded by at least afactor of 9, for example, to the outer border of the peripheral routingcells shown in detail view 233 and marked by bold lines within W16 block230. If the components of transfer cell W1 may be implemented in anon-square region, the outer boundary may potentially be expandedfurther in the X dimension and/or Y dimension, (e.g., extending into anarea covered by up to 16 routing cells). Also, while a square aspectratio (i.e., width/length ratio) is shown for W16 block 230 andindividual cells therein, other aspect ratios may apply in alternativeembodiments, including aspect ratios in which cell implementation areamay be optimized by different layout patterns. Further, while shown inthe context of a W16 block, the transfer cell layout of FIG. 5 may alsobe employed within the R16 block.

Reflecting on the different interface configurations shown in FIG. 1B(and FIGS. 3A-3E), it can be seen that the longest transfer path length,and thus the transfer path having the longest propagation time, occursin the ×1 configuration, when signals are laterally transferred acrossthe width of the physical interface, between a source I/O node at oneend and a destination register at the opposite end. And while bufferamplifiers may be employed within individual transfer cells (e.g., asshown by transfer buffer 145 of FIG. 1A), timing skew or othersynchronization problems resulting from the overall lateral transfertime may undesirably constrain the practicable lateral transfer distanceand thus the maximum-to-minimum width ratio of the signaling interface.

FIG. 6A illustrates an alternative lateral transfer structure, referredto herein as a “centered I/O” embodiment, that enables the lateraltransfer distance within the worst-case transfer configuration (e.g.,×1) to be cut in half (or approximately so), thus substantially reducingthe transfer propagation delay. In effect, by redesigning the transfercells shown at 130 and 140 to enable bidirectional signal transfer ineither direction along the segmented lateral transfer path, it becomespossible to establish an I/O node centrally disposed within a cluster ofother unused I/O nodes as the source/destination I/O node (i.e., theactive I/O node) for the corresponding cluster of core registers. FIG.6A illustrates this effect, contrasting the unidirectional lateraltransfer approach shown in FIGS. 1B and 3A-3E, with a bidirectionallateral transfer approach for each of four logical interface widthconfigurations. As shown, for each single-source cluster of ‘M’ I/Onodes (i.e., group of I/O nodes having a single active I/O node and M−1inactive I/O nodes), the active I/O node is selected to be I/O nodeM/2+1, where ‘/’ denotes integer division and assuming that the I/Onodes are numbered sequentially from the bottom to the top of thecluster. Thus, in the ×8 configuration, where no single-source I/Ocluster exists (i.e., all I/O nodes are active), data signals are routedidentically in both the unidirectional and bidirectional transfer cases,as no lateral transfer occurs. By contrast, in the ×1 configuration,where the unilateral lateral transfer embodiment requires lateraltransfer across the entire length of the physical interface, between thebottom-edge I/O node 0 and the top-edge core register 7, the centeredI/O approach enables transfer from a centered I/O node 4 (i.e., 7/2+1)in both lateral directions (i.e., bilateral or bidirectional transfer)to the destination registers (0 and 7) at either end of the interface.As shown, this bidirectional lateral transfer from a centered I/O nodecuts the maximum lateral transfer path approximately in half, relativeto the unidirectional-transfer embodiment, thereby approximately halvingthe signal propagation time.

While the propagation time reduction is most notable in the narrowestwidth configuration (i.e., where the lateral transfer path or paths arelongest), the transfer propagation time is also reduced in other logicalwidth configurations. For example, in the ×2 width configuration, I/Onodes [2] and [6] are selected as the centered I/O's within respectivesingle-source clusters of four I/O nodes, thus reducing the lateraltransfer distance relative to the unidirectional lateral transferarrangement. In the ×4 example, in which the single-source I/O clustersize is two, the lateral transfer distance is unidirectional regardlessof the I/O node selected (i.e., there is only one lateral transferdestination) and in the native width, there is no lateral transfer atall.

FIG. 6B illustrates embodiments of bidirectional transfer cells 307 and317 that may be employed within a bidirectional lateral transferstructure 300 to enable the interface width configurations shown in FIG.6A. Bidirectional transfer cell 307 is implemented in generally the samemanner as the unidirectional transfer cell (130) shown in FIG. 1A,except that independent select-up and select-down signals, Su and Sd,are supplied to the I/O and transfer switching elements 309 and 311 (andthus separate inverter elements 310, 312 are provided to generatecomplementary instances of the select signal). By this arrangement, bothswitching elements may be switched on concurrently (raising theselect-up and select-down signals, Su and Sd) to enable an active, localI/O node (i.e., the center I/O node within a single-source cluster) todrive an input signal in both directions, up and down along the lateraltransfer path and thus to core registers corresponding to inactive I/Onodes on either side of the active I/O node. As discussed, alternativestructures may be used to implement the switching elements 309, 311 andbuffer amplifiers may be provided to limit the t_(RC) delay along widerinterfaces.

The embodiment at 317 may be employed in applications where bufferamplifiers or other generally unidirectional circuit elements aredesirable. As shown, the lateral transfer path is split into isolatedupper and lower segments, Yu and Yd, each of which is either (i)undriven, (ii) driven according to the state of local input (W_(I)), or(iii) driven according to the state of a signal present on alternatetransfer path segment (i.e., Yu driving Yd or vice-versa). Morespecifically, upper- and lower-segment drivers 320, 322 may beselectively enabled by enable signals Eu and Ed, respectively, to driveor refrain from driving a signal onto the upper and lower path segments,and upper- and lower-segment multiplexers 319 and 321 are controlled byrespective select signals Su and Sd, to select either the local input,W_(I), or the alternate transfer path segment as the signal source foran enabled segment driver (note that select signals Su and Sd will notnecessarily have the same logic values within cell 317 as within cell307 for a given width configuration). By this arrangement, bidirectionaltransfer cell 317 can be put into at least the following states, each ofwhich is employed in one or more of the interface configurations shownin FIG. 6A:

-   -   Direct Output (Eu=1, Su=1, Ed=0, Sd=x, where ‘x’ indicates        “don't care”): local input selected by upper segment multiplexer        and driven onto upper path segment, while lower path segment is        undriven;    -   Bidirectional Output (Eu=1, Su=1, Ed=1, Sd=1): local input        selected by upper- and lower-segment multiplexers and driven        onto both the upper and lower path segments;    -   Transfer-Up (Eu=1, Su=0, Ed=0, Sd=x, where ‘x’ indicates don't        care): signal present on lower path segment driven onto upper        path segment, thus effecting an upward lateral transfer;    -   Transfer-Down (Ed=1, Sd=0, Eu=0, Su=x): signal present on upper        path segment driven onto lower path segment, thus effecting a        downward lateral transfer; and    -   Isolation: upper and lower transfer path segments undriven        (Eu=0, Ed=0, Su=x, Sd=x).

Referring to the bilateral-transfer interface configurations shown inFIG. 6A, for example, in the ×8 configuration, each transfer cell is setto the direct output state to drive the upper transfer path segmentaccording to the local input and to leave the lower transfer pathsegment undriven (thereby avoiding conflict with the transfer cellbelow).

In the ×4 configuration, each of the bidirectional transfer cellscorresponding to an active I/O node is set to the bilateral output stateto drive both upper and lower transfer path segments according to thestate of the local input, thus delivering the input data to the localoutput (W_(O)) and to the local output of the immediately downstreamtransfer cell. By contrast, each of the bidirectional transfer cellscorresponding to inactive I/O nodes (i.e., the cells immediatelydownstream from respective “active-node transfer cells”) are set to theisolation state, thus avoiding contention with adjacent cells or,viewed, alternatively, isolating each dual-I/O cluster (i.e.,single-source I/O cluster having one active I/O node and one inactiveI/O node) from the others.

In the ×2 interface configuration, each of the bidirectional transfercells corresponding to an active I/O node is again placed in abidirectional output state, while, while the transfer cells immediatelyabove and below a given bidirectional-output transfer cell are set totransfer-up and transfer-down states, respectively, and the bottomtransfer cell in each quad-I/O cluster (i.e., cluster formed by I/Onodes 0-3 or cluster formed by I/O nodes 4-7) is set to an isolationstate.

Similarly, in the ×1 interface configuration, the bidirectional transfercell corresponding to the sole active I/O node (i.e., central I/O node 4in this example, although node 3 may alternatively be used) is set tothe bilateral output state, while all transfer cells above are set tothe transfer-up state and all transfer cells below are set to thetransfer-down state (except optionally the transfer cell correspondingto the bottom-edge I/O node, which may be set to the isolation state),thereby enabling data to be conveyed between the I/O node centeredwithin the interface and the core registers above and below.

FIG. 7 illustrates a further reduction in lateral transfer bandwidthenabled by the centered I/O approach described in reference to FIGS. 6Aand 6B. More specifically, recognizing that data conveyed in areduced-width interface configuration is loaded sequentially intorespective core registers, it occurs that, instead of transferring anincoming data word upward or downward to a given core register during aregister-load interval (i.e., following the load sequence shown at 342carried out within interface 343), the incoming data may be split intoupper and lower portions, with the upper portion being transferredupward and the lower portion being transferred downward during each dataload interval. By partially remapping the data destination (or coreregister load sequence) in this way, only half of any incoming data wordneed be transferred in a given direction (up or down) by the lateraltransfer structure, thus halving the required lateral transfer bandwidth(i.e., halving the number of signal conductors). For example, if theserialization/deserialization ratio (‘n’) effected within the datatransceiver circuitry is 16, then the number of lateral transferconductors required within the bidirectional, segmented lateral transferstructure may be reduced from 16 to 8. And while incoming write data is,in effect stored in different physical locations as a result of theremapped core register destinations, this change may be accommodated solong as all data read from the memory device follows the same mapping asdata written to the memory device. That is, the association (mapping)between memory address and physical location of the accessed storagecells may be changed without adverse consequence so long as read andwrite operations directed to the same memory address access the samedata. Thus, by remapping the data destinations within the core loadsequence, the shared-route load sequence 342 in which n/2-bit wideportions (‘A’ and ‘B’ in FIG. 7) of an incoming data word are routedside-by-side along an n-conductor lateral transfer path 301 may bereplaced by the split-route load sequence 344 within interface 345 inwhich n/2-bit wide portions of each incoming data word are routed inopposite directions, up and down, along respective n/2-conductorsegments of lateral transfer path 341, thus halving the width of thelateral transfer structure with negligible overhead.

Still referring to FIG. 7, transfer cell embodiments that may be used tosupport the split-route load sequence are illustrated at 365 and 375. Intransfer cell 365, a pair of I/O switching elements 367 and 371 aresupplied to enable respective “up” and “down” portions of an input dataword, Wiu and Wid, to be coupled to respective up and down segments (Yuand Yd, also referred to herein as upper and lower segments,respectively) of a lateral transfer path. A through-cell switchingelement 369 is also provided to enable the upper and lower transfer pathsegments to be coupled to one another, and a multiplexer, formed byswitching elements 372 and 373 is provided to select the signal presenton either the upper or lower path segment to drive the lower portion ofthe local data output, Wod. The upper portion of the local data output,Wou, is coupled to upper transfer path segment, Yu, and is thus drivenby the signal delivered to the upper path segments via switchingelements 367, 371 and/or 369 or by counterpart switching elements in thetransfer cell above. Select signals, Su and Sd (select-up andselect-down) are supplied to control inputs (e.g., gates) of I/Oswitching elements 367 and 371, and thus control coupling of the upperand lower local data inputs (Wiu, Wid) to the upper and lower transferpath segments, respectively. Enable signal Et (enable-through) isapplied to control input(s) of switching element 369 to enable the upperand lower path segments to be switchably coupled to or decoupled fromone another, and select signal, Sc (select-common), is used to controlthe operation of the output multiplexer (i.e., multiplexer formed byswitching elements 372 and 373), enabling the signal present on thelower path segment to drive the lower data output (Wod), or enabling thesignal present on the upper path segment to drive the upper and lowerdata outputs (Wou, Wod) in common.

Transfer cell 375 enables the same functional path connections astransfer cell 365, but includes buffer amplifiers 382, 385 and othergenerally unidirectional circuit elements to mitigate, for example,transfer-distance-dependent t_(RC). For example, upper and lower segmentmultiplexers 377, 379 and upper and lower segment drivers 378 and 380(e.g., tri-state drivers) enable the data-source select operations andswitched through-connection provided by switching elements 367, 369 and371 within transfer cell 365, and output multiplexer 381 corresponds toswitching elements 372 and 373. Further, the segment multiplexers 377,379 and segment drivers 378, 380 correspond to the segment multiplexers319, 321 and segment drivers 320, 322 shown in transfer cell 317 of FIG.6B, except that the input data source is split into upper and lowerportions (Wiu and Wid), and the upper and lower transfer path segments(Yu and Yd) are half as wide as their counterparts in transfer cell 317as only half as much data is transferred in a given direction throughtransfer cell 375.

Each of the transfer cell embodiments 365, 375 shown in FIG. 7 may beset to the following states to support different logical interface widthconfigurations (note that, though its logic state is not specificallyshown below, enable-through signal, Et, my be expressed as(Ed*/Sd)+(Eu*/Su), where denotes logical AND, ‘+’ denotes logical OR,and ‘/’ denotes logical NOT):

-   -   Direct Output (Eu=1, Su=1, Ed=0, Sd=x, Sc=0): upper portion of        local input selected by upper segment multiplexer and driven        onto upper transfer path segment (and thus to upper local core        register), lower portion of local input forwarded to lower core        register via output multiplexer, and lower transfer path segment        undriven;    -   Bidirectional Output (Eu=1, Su=1, Ed=1, Sd=1, Sc=1): upper and        lower portions of local input selected by upper- and        lower-segment multiplexers and driven onto both the upper and        lower path segments, respectively;    -   Transfer-Up (Eu=1, Su=0, Ed=0, Sd=x, Sc=1): signal present on        lower path segment driven onto upper path segment, thus        effecting an upward lateral transfer;    -   Transfer-Down (Ed=1, Sd=0, Eu=0, Su=x, Sc=1): signal present on        upper path segment driven onto lower path segment, thus        effecting a downward lateral transfer; and    -   Isolation: upper and lower transfer path segments undriven, and        upper path segment coupled in common to upper and lower data        outputs (Eu=0, Ed=0, Su=x, Sd=x, Sc=1).

FIG. 8 illustrates an embodiment of a ×16 signaling interface 400modified relative to signaling interface 175 of FIG. 2 to includesplit-route, bidirectional transfer cells W2 (i.e., transfer cellscorresponding to transfer cell 375 of FIG. 7). As shown at 403, a set ofeight W2 transfer cells, each receiving upper and lower write data inputbits (Wiu, Wid) are applied in place of the 16, single-input-bit W1cells shown in FIG. 2. A single lateral transfer conductor formed byupper and lower segments, Yu and Yd, is coupled to each W2 transfercell, so that the constituent number of conductors (and thus thephysical width) within the segmented lateral transfer path is reducedfrom 16 (in FIG. 2) to 8, and thus the block of eight W2 cells isreferred to as a “W8 block.” Schematically, each W8 block may be viewedas an instance of the W2 cell in which each input (Wiu or Wid), output(Wou or Wod) and transfer path segment (Yu or Yd) is eight bits wide.The routing cell, W0, I/O nodes (“DQ”) and core may be implementedgenerally as described in reference to FIG. 2, though the DQ and coreregisters shown at 199 and 411, respectively, are each depicted ashaving two constituent registers and corresponding pairs of output pathsand input paths to emphasize that two portions of data are beingseparately routed within the set of sixteen W8 blocks that form thesegmented lateral transfer circuitry.

FIGS. 9A-9E illustrate exemplary interface widths enabled by thesplit-route, bilateral transfer blocks W8 of FIG. 8, and thetransfer-state control signals (Eu, Su, Ed, Sd, Sc, as shown at 415)applied to each of the W2 transfer cells 375 therein. For example, inthe ×16 configuration, each W8 transfer cell block (numbered 0-15 frombottom to top) is set to the direct output state to drive the upperportion of the input data to the upper local core register via the uppertransfer path segment, and to drive the lower portion of the input datato the lower local core register via the output select multiplexer(i.e., element 381 of FIG. 7). In this configuration, no lateraltransfer is effected in either direction, and instead the local writedata is supplied to the local core registers for each W8 transfer block.

In the ×8 configuration, each W8 transfer block corresponding to anactive I/O node is set to the bilateral output state to drive both upperand lower transfer path segments according to the state of the localinput, thus delivering the upper portion of the local input data incommon to the upper and lower local core registers, and laterallytransferring the lower portion of the local input data to the downstream(i.e., lower and adjacent) W8 block for delivery to the upper and lowercore registers for that transfer block. By contrast, each of the W8transfer blocks corresponding to inactive I/O nodes (i.e., the W8 blocksimmediately downstream from respective “active-node transfer blocks”)are set to the isolation state, thus avoiding contention with adjacentW8 blocks or, viewed, alternatively, isolating each of eight dual-I/Oclusters (i.e., single-source I/O cluster having one active I/O node andone inactive I/O node) from the others.

In the ×4 interface configuration, each of the W8 transfer blockscorresponding to an active I/O node is again placed in a bidirectionaloutput state, while the W8 transfer blocks immediately above and beloware set to transfer-up and transfer-down states, respectively, and thebottom W8 transfer block in each quad-I/O cluster (i.e., cluster formedby I/O nodes 0-3, 4-7, 8-11, or 12-15) is set to an isolation state.

Similarly, in the ×2 interface configuration, each of the W8 transferblocks corresponding to an active I/O node is placed in a bidirectionaloutput state, while the three W8 transfer blocks immediately above andbelow are set to transfer-up and transfer-down states, respectively, andthe bottom W8 transfer block in each eight-I/O cluster (i.e., clusterformed by I/O nodes 0-7 or 8-15) is set to an isolation state.

Lastly, in the ×1 interface configuration, the W8 transfer blockcorresponding to the sole active I/O node (i.e., central I/O node 8 inthis example, although node 7 may alternatively be used) is set to thebilateral output state, while all transfer cells above are set to thetransfer-up state and all transfer cells below are set to thetransfer-down state (except optionally the transfer cell correspondingto the bottom-edge I/O node, which may be set to an isolation state),thereby enabling respective upper and lower portions of the input datato be conveyed between the I/O node centered within the interface andthe core registers above and below.

FIG. 10 illustrates an expanded view of an 8-I/O single-source clusterwithin the ×2 configuration shown in FIG. 9D to provide an appreciationof the upward and downward transfer routing enabled by the split-route,bidirectional transfer cells within each W8 transfer block.

FIG. 11 illustrates an alternative layout of W2 cells within a W8transfer block 430 that increases the die area available for W2 cellimplementation. Viewing the eight W2 cells as a 2×4 cell array that isto be distributed within the 8×8 W8 block, then each W2 cell may bedisposed four array positions (i.e., the number of available cellpositions along the X axis, 8, divided by the number of W2 cells to bedisposed along that axis, 2) from its neighbor in an adjacent row andtwo array positions (Y axis dimension, 8, divided by W2 cells to bedistributed (4)) from its neighbor in an adjacent column. The eightupper and lower transfer path segments, Yu and Yd, are remappedaccordingly as shown by the signal group numbering along the upper andlower edges of the W8 block. By this arrangement, the die area availablefor implementation of the multiplexing elements, tri-state drivers andbuffer amplifiers within each W2 cell 375 is substantially expanded, forexample, to the outer border of the peripheral routing cells (W0) shownin detail view 431 and marked by bold lines within W8 block 430. Also,while a specific aspect ratio is shown for the W8 block and individualW2 and W0 cells therein, other aspect ratios may apply in alternativeembodiments, including aspect ratios in which cell implementation areamay be optimized by different layout patterns. Further, while shown inthe context of a W8 block, the transfer cell layout of FIG. 11 may alsobe employed within the R8 block discussed below.

FIG. 12 illustrates an embodiment of a split-route, bidirectionaltransfer cell R2 465 that may be used within the read data path of ×16IC signaling interface 400. That is, the R2 cells may be disposed,together with routing cells R0, within an R8 block as shown at 453 toeffect the split-route, bidirectional transfer operation generallydescribed in reference to FIGS. 6A, 6B and 7.

In contrast to the write-data transfer cells (e.g., described inreference to FIGS. 7 and 8) which effect a data fan-out within asingle-source I/O cluster, the read-data transfer cells 465 perform aserialization or multiplexing function. Thus, while the select/enablesignals used to establish the state of the write-data transfer cells maybe maintained in a steady state for a given logical width configuration(e.g., fanning-out data to all core registers, with the core registerload sequence being controlled by other logic within the core), theselect/enable signals used to establish the state of the read-datatransfer cells may be transitioned during sub-column-cycle intervals toestablish a multiplexed path between different sets of core registers477 and the read data registers 209 of an active I/O node. Further,within the split-routing embodiment shown, the upper-data and lower-dataregisters 477 u, 477 d that constitute a given core register 477 may bealternately selected as a read data source, as shown in detail view 475.In the embodiment of FIG. 12, this selection between upper and lowercore register data sources is performed by multiplexer 479 (depicted asbeing part of a core register 477, though the multiplexer mayalternatively be deemed a constituent of the R2 cell 465), whichsupplies input signal Rid/Rud (“Riud”) to one input of the R2 cell. Asshown, the R2 cell additionally receives input Riu directly from theupper register 477 u of the core data register pair, and otherwiseincludes upper and lower segment multiplexers 467, 469 and upper andlower segment drivers 468, 470 (i.e., tri-state drivers) to controlsignals enabled onto upper and lower transfer segment paths, Zu and Zd,in generally the manner described in reference to transfer cell 375 ofFIG. 7. An output multiplexer 471 is also provided to enable either theupper path segment, Zu (via buffer 473), or the upper core register 477u to be the source of the signal driven onto upper data output, Rou. Thelower data output, Rod, is driven via buffer 472 according to the signalpresent on lower path segment, Zd. By this arrangement, the followingstates may be achieved to support different interface widthconfigurations, and different multiplexed paths within those widthconfigurations:

-   -   Direct Output (Eu=1, Su=1, Ed=0, Sd=x, Sc=0): upper data from        local core register delivered to upper data output (Rou) via        output multiplexer (471), multiplexed data input (Riud) from        local core register (i.e., signal output via core-register        multiplexer 479) selected by lower segment multiplexer and        driven onto lower transfer path segment for delivery to lower        data output (Rod), and upper transfer path segment undriven;    -   Semi-Drive (Upper): (Eu=1, Su=1, Ed=0, Sd=x, Sc=1): multiplexed        data input (Riud) driven onto upper transfer path segment for        delivery to either local upper output (via output multiplexer)        or lower output of upstream transfer cell, while lower transfer        path segment undriven;    -   Semi-Drive (Lower): (Eu=0, Su=0, Ed=1, Sd=1, Sc=1): multiplexed        data input (Riud) driven onto lower transfer path segment for        delivery to upper output of downstream cell (i.e., via output        multiplexer within that cell) while upper transfer path segment        is undriven;    -   Transfer-Up (Eu=1, Su=0, Ed=0, Sd=x, Sc=x): signal present on        lower path segment driven onto upper path segment, thus        effecting an upward lateral transfer;    -   Transfer-Down (Ed=1, Sd=0, Eu=0, Su=x, Sc=x): signal present on        upper path segment driven onto lower path segment, thus        effecting a downward lateral transfer; and    -   Isolation: upper and lower transfer path segments undriven, and        upper path segment coupled in common to upper and lower data        outputs (Eu=0, Ed=0, Su=x, Sd=x, Sc=1).

FIGS. 13A-13E illustrate exemplary interface widths enabled by thesplit-route, bilateral transfer blocks R8 of FIG. 12, and the statecontrol signals (Eu, Su, Ed, Sd, Sc, as shown at 490) applied to each ofthe R2 transfer cells therein. For example, in the ×16 configurationshown in FIG. 13A, each R8 transfer cell block (numbered 0-15 frombottom up) is set to the direct output state to deliver the data fromthe upper local core register (element 477 u of FIG. 12) to the upperread-data register of the local I/O node via the output multiplexer 471within each R2 cell, and to deliver the data from the lower local coreregister (element 477 d of FIG. 12) to the lower read-data register ofthe local I/O node via the lower transfer path segment (i.e., via lowersegment multiplexer 469 and lower segment driver 470). In this widthconfiguration, no lateral transfer is effected between the R8 cells,and, because data need not be multiplexed to a single I/O node frommultiple core registers, the transfer-state control signals may remainin the steady state shown.

In the ×8 configuration depicted in FIG. 13B, each R8 transfer block isoperated the upper semi-drive state to deliver core data (i.e., eitherupper or lower data from the corresponding core register, according, forexample, to the state of a sub-column address bit) onto a respective oneof the sixteen upper transfer path segments (Zu in FIG. 12). Because theupper transfer path segment for each R8 transfer block is coupled to thelower transfer path segment for the block above, core data from eitherthe upper half or lower half of all sixteen core registers is deliveredconcurrently to the upper and lower data outputs for the eight activeI/O nodes. As in the ×16 configuration, no path multiplexing occurswithin the R8 transfer blocks, so the transfer-state control signals mayremain at the steady states shown.

In the ×4 configuration (FIG. 13C), each R8 transfer block is operatedin either an upper semi-drive state or lower semi-drive state to delivercore data to a selected (active) I/O node centered within a four-nodecluster. Further, the segment multiplexers and/or segment drivers of R8blocks that deliver data to the active I/O node via a shared segment ofthe lateral transfer path are alternated between states that enable datafrom different core register sources to be time-multiplexed to a givenI/O node in respective half cycles via the shared transfer path segment.Referring to the cluster of four R8 blocks corresponding to I/O nodes12-15, for example (i.e., R8 transfer blocks corresponding to the topfour I/O nodes and referred to as R8 blocks 12-15), data from the coreregisters corresponding to R8 blocks 14 and 15 are time multiplexed ontothe upper transfer path segment within R8 block 14 (i.e., a sharedtransfer path segment), and data from the core register corresponding toR8 blocks 12 and 13 are time multiplexed onto the upper transfer pathsegment within R8 block 13 (and also the lower segment path within R8block 14). Accordingly, during the first half of a memory access cycle(e.g., a column read cycle), R8 blocks 15 and 13 are set to lower andupper semi-drive states, respectively, to deliver data to the upper andlower data outputs of active-node R8 block 14 (i.e., the R8 blockcorresponding to shaded I/O node, 14), while R8 blocks 12 and 14 are setto an isolation state. In the second half of the memory access cycle, bycontrast, R8 transfer blocks 12 and 14 are set to semi-drive states(upper) to deliver data to the upper and lower data outputs of R8 block14, while R8 transfer block 15 is set to an isolation state (thusavoiding contention with the data output from transfer block 14) and R8block 13 is set to a transfer-up state (thus passing the data from R8block 12 to the lower data output of R8 block 14. The remaining 4-blockclusters of R8 blocks (0-3, 4-7, 8-11) are operated in the same manneras R8 blocks 12-15. Note that instead of being switched betweensemi-drive and isolation states, the bottom block in each 4-blockcluster (i.e., R8 blocks 0, 4, 8 and 12) may be left statically in thesemi-drive (upper) state throughout the memory access cycle as uppersegment multiplexer in the immediately upstream R8 block (i.e., in R8blocks 1, 5, 9 and 13) isolates the upper transfer segment of the bottomblock during the first half of the memory access cycle.

In the ×2 configuration (FIG. 13D), each R8 transfer block is operatedin either an upper semi-drive state or lower semi-drive state to delivercore data to a selected (active) I/O node centered within an eight-nodecluster. As shown by the state control diagram presented beneath the×2-configured interface, the segment multiplexers and/or segment driversof R8 blocks that deliver data to the active I/O node via sharedsegments of the lateral transfer path are alternated between states thatenable data from different core register sources to be time-multiplexedto a given I/O node in respective quarters (fourths) of a memory accesscycles via the shared transfer path segment. Referring to the cluster ofeight R8 blocks 8-15, for example, data from the core registerscorresponding to R8 blocks 12-15 are time multiplexed onto the uppertransfer path segment within R8 block 12, and data from core registerscorresponding to R8 blocks 8-11 are time multiplexed onto the uppertransfer path segment within R8 block 11 (and thus onto the lowersegment path within R8 block 12). Accordingly, during the first quarterof a memory access cycle (e.g., a column read cycle), R8 blocks 15 and11 are set to lower and upper semi-drive states, respectively, todeliver data to the upper and lower data outputs of active-node R8 block12 (i.e., the R8 block corresponding to shaded I/O node). To supportthis transfer, R8 block 12 is isolated, R8 blocks 13 and 14 are set totransfer-down states, and R8 blocks 8, 9 and 10 are set to transfer-upstates. During the second quarter of the memory access cycle, R8 blocks14 and 10 are switched to lower and upper semi-drive states,respectively, while R8 block 11 is switched to a transfer-up state.During the third quarter of the memory access cycle, R8 blocks 13 and 9are switched to lower and upper semi-drive states, respectively, whileR8 block 10 is switched to a transfer-up state, and during the fourthand last quarter of the memory access cycle, R8 blocks 12 and 8 areswitched to upper semi-drive states, respectively, while R8 block 9 isswitched to a transfer-up state and R8 block 13 is isolated (thuspreventing contention with the semi-drive state of R8 block 12). Theremaining 8-block cluster, R8 blocks 0-7, may be operated in the samemanner as R8 blocks 8-15. Further, although a particular set of statecontrols is shown, any R8 block that is decoupled from a shared transferpath segment by the state of an R8 block closer to the center of thecluster (i.e., closer to the active I/O node) may optionally be left ina semi-drive state, transfer state or isolation state. Also, while aparticular time-multiplexing order has been shown (e.g., sourcing datafrom core registers corresponding to R8 blocks 15|11, 14|10, 13|9 andthen 12|8), different time-multiplexing orders may be used inalternative embodiments.

In the ×1 configuration (FIG. 13E), the complete set of 16 R8 transferblocks are operated in upper/lower semi-drive states to deliver coredata to the I/O node corresponding to R8 block 8, the I/O node centeredwithin the overall physical interface. As shown by the state controldiagram presented below the ×1 configured interface, the segmentmultiplexers and/or segment drivers of R8 blocks that deliver data tothe active I/O node via shared segments of the lateral transfer path areswitched between states that enable data from different core registersources to be time-multiplexed to the active I/O node in respectiveeighths of a memory access cycle. Accordingly, during the first eighthof a memory access cycle (e.g., a column read cycle), R8 blocks 15 and 7are set to lower and upper semi-drive states, respectively, to deliverdata to the upper and lower data outputs of active-node R8 block 8. Tosupport this transfer, R8 block 8 is set to the isolation state, R8blocks 9-14 are set to transfer-down states, and R8 blocks 0-6 are setto transfer-up states (or, alternatively, set to isolation states as R8blocks 0-6 are unused during the first portion of the memory accesscycle). During the second eighth of the memory access cycle, R8 blocks14 and 6 are switched to lower and upper semi-drive states,respectively, while R8 block 7 is switched to a transfer-up state.Similarly, during the third eighth of the memory access cycle, R8 blocks13 and 5 are switched to lower and upper semi-drive states,respectively, while R8 block 6 is switched to a transfer-up state;during the fourth eighth of the memory access cycle, R8 blocks 12 and 4are switched to lower and upper semi-drive states, respectively, whileR8 block 5 is switched to a transfer-up state; during the fifth eighthof the memory access cycle, R8 blocks 11 and 3 are switched to lower andupper semi-drive states, respectively, while R8 block 4 is switched to atransfer-up state; during the sixth eighth of the memory access cycle,R8 blocks 10 and 2 are switched to lower and upper semi-drive states,respectively, while R8 block 3 is switched to a transfer-up state;during the seventh eighth of the memory access cycle, R8 blocks 9 and 1are switched to lower and upper semi-drive states, respectively, whileR8 block 2 is switched to a transfer-up state; and during the finaleighth of the memory access cycle, R8 blocks 8 and 0 are switched tolower and upper semi-drive states, respectively, while R8 block 1 isswitched to a transfer-up state, and R8 block 9 is switched to anisolation state (to avoid contention with the semi-drive state of R8block 8). As discussed above, while a particular set of state controlsis shown, any R8 block that is decoupled from a shared transfer pathsegment by the state of an adjacent R8 block closer to the center of thecluster may optionally be left in a semi-drive state, transfer state orisolation state. Also, data may be time-multiplexed from the variouscore registers in different order in alternative embodiments.

FIG. 14 illustrates an expanded view of an 8-I/O single-source clusterwithin the ×2 configuration shown in FIG. 13D to provide an appreciationof the upward and downward transfer routing enabled by the split-route,bidirectional transfer cells within each R8 transfer block. Reflectingon FIGS. 10 and 14, which illustrate segmented lateral transferstructures dedicated to write-data and read-data transfer, respectively,it should be noted that constituent components within either of transferstructures (including the transfer path segments themselves) may be usedto convey both write and read data, thus reducing the amount ofcircuitry and signal conduction paths required, and thus furtherimproving the area efficiency of the adjustable-width signalinginterface. More generally, such resource sharing may be employed in anycounterpart read and write data transfer structures disclosed herein.Additionally, the various buffer amplifiers, tri-state drivers and anyother power-consuming elements of the various segmented lateral transferstructures disclosed herein may be disabled for power-conservationpurposes during idle periods, including brief periods interspersedbetween memory access operations in which the lateral transferstructures are used to convey data between the PHY, as well as variouslow-power modes that may be employed within the host integrated circuitcomponent.

FIGS. 15A-15C illustrate embodiments of memory systems havingadjustable-width memory components that may employ any of the segmentedlateral transfer paths as described herein. Each of the memory systemsincludes a memory controller component configured to manage memoryaccess transactions with one or more memory components. In theembodiment of FIG. 15A, for example, a single transaction queue 505within memory controller 503 manages memory access transactions (e.g.,issuance of memory access commands and corresponding read/write datatransfer) with respect to a memory component 501 configured to have anative (or full-width) data interface. In the example shown, thefull-width memory-side data interface is a ×16 interface coupled to 16data links (i.e., four link interface groups DQ-A, DQ-B, DQ-C and DQ-Deach coupled to a respective set of four data links) in which data istransmitted at a 3.2 Gb/s (e.g., in response to rising and falling edgesof a 1.6 GHz clock, or rising edges of two complementary 1.6 GHzclocks), thereby establishing a total data interface bandwidth of 6.4GB/s (6.4 gigabytes per second). A three-bit-wide memory-side CAinterface (CA-X) is used to receive and forward memory commands (e.g.,row activation commands and column read/column write commands in a DRAMcomponent) and address values to command/address control logic 513,which in turn issues row and column access control and address signals(CA-Row, CA-Col) to an address-selected storage bank within the memorycore (e.g., banks 0A/B-7A/B). As shown, the memory core, which may bedeemed to include control logic 513, operates at a 200 MHz (0.2 GHz)column cycle rate (i.e., column read/write operations are carried out on5 nS intervals) which establishes the core clock frequency and thus a16:1 read data serialization ratio (or 1:16 write data deserializationratio) within the link transceivers 514. Accordingly, 16 bits of dataper signaling link are provided to or from the memory core in a givencolumn read or write operation, thus establishing a 256-bit (32 byte)column access granularity. Data to be retrieved as part of a column readoperation is output from the address-selected bank (and storage row andcolumn) to lateral transfer structures 511 and, in the native-widthconfiguration shown, delivered directly data transceivers 514 fortransmission to memory controller 503 via the sixteen data links. Thatis, the lateral transfer structure is configured as shown, for example,in FIGS. 9A and 13A, to implement the ×16 data interface. Transceivers521 within memory controller 503 receive the incoming read data anddeliver the data to temporary storage buffers within (or associatedwith) transaction queue 505 for eventual output to a memory requester(which may be included within the same IC as the memory controller ormay be different IC). Write data is conveyed from memory controller 503to memory component 501 follows essentially the reverse path of the readdata, from controller-side transceivers 521 to memory-side transceivers514, through the lateral transfer structure 511 for storage within anaddress selected storage bank, row and column.

In one embodiment, the command/address logic 513 within memory component501 includes a programmable mode register 525 having an interface widthfield 527. The memory controller programs the mode register, forexample, by issuing a register-write command and corresponding registervalue via the command/address path (although the register value mayalternatively be issued via one or more data links). Memory component501 responds to the register-write command by loading the register valueinto the mode register (which may include multiple registers), includingloading an interface width setting into interface width field 527. Theinterface width setting is supplied to interface control circuitrywithin command/address logic 513 which responsively outputs staticand/or dynamic transfer-state control signals 516 corresponding to thespecified interface width (e.g., as described in reference to FIGS.9A-9E and 13A-13E) to lateral transfer circuitry 511.

In the embodiment shown, the interface width setting is a three-bit codehaving one of five values to establish the different logical widthsshown (i.e., ×16, ×8, ×4, ×2, ×1, though more or fewer widthconfigurations may apply in alternative embodiments). In the memorycomponent shown, the lateral transfer structure 511 implements asplit-route, bilateral transfer operation and thus effects a centeredI/O arrangement as discussed above. That is, as shown in the table at528, the active I/O pins (or other interconnects) for each logical widthnarrower than the native width of the memory component (i.e., ×8 andbelow in the example shown) are mutually exclusive. For example, none ofthe active I/O pins in any logical width configuration of ×8 or narroweris used in any other logical width configuration of ×8 or narrower.Thus, each register programming operation that sets a logical widthnarrower than the native width of the memory device enables datatransfer via an exclusive subset of the I/O pins of memory component 501(i.e., pins that are unused in any other logical width narrower than thenative width of the memory device).

In the embodiment of FIG. 15B two memory components 501A and 501B areconfigured to have ×8 logical interface widths (e.g., by establishingthe lateral transfer paths shown in FIGS. 9B and 13B, with I/O nodes 1,3, 5 and 7 corresponding to DQ-A and I/O nodes 9, 11, 13 and 15corresponding to DQ-C). Even-numbered controller-side data interfacenodes DQ-0 and DQ-2 are coupled via respective data signaling links toI/O nodes DQ-A and DQ-C within memory component 501A, and odd-numberedcontroller-side data I/O nodes DQ-1 and DQ-3 are coupled to I/O nodesDQ-A and DQ-C within memory component 501B. Separate transaction queues531A, 531B are maintained for the two different memory components, withtransaction queue 531A supplying command/address values to memorycomponent 501A via a first set of CA links (i.e., driven bycontroller-side CA interface, CA-0), and transaction queue 531Bsupplying C/A values to memory component 501B via a second set of CAlinks (driven by controller-side CA interface, CA-1). The even-numberedand odd-numbered controller-side data I/O nodes are coupled to receivewrite data from and deliver read data to storage buffers within (orassociated with) transaction queues 531A and 531B, respectively. By thisarrangement, the 6.4 GB/s bandwidth of the memory system is maintained,but split between two separately addressed memory components 501A, 501B,thereby establishing a 16B column access granularity within each memorycomponent.

FIG. 15C illustrates an alternative memory system embodiment involvingthe same memory components shown in FIG. 15B, but configured forshared-command operation. That is, each of memory components 501A, 501Bis configured to have a ×8 interface width (e.g., by establishing thelateral transfer paths shown in FIGS. 9B and 13B, with I/O nodes 1, 3, 5and 7 corresponding to DQ-A and I/O nodes 9, 11, 13 and 15 correspondingto DQ-C), but a single transaction queue 555 within memory controller553 is used to source commands to the memory components (therebyoperating the two components in lock step) and to send/receive datato/from each. Though respective command/address drivers 556A, 556B areprovided to output command/address values to the two memory components,this is not necessary in all cases. Rather, a single command/addressoutput from memory controller 553 may be routed to both memorycomponents 501A, 501B (i.e., command inputs of the memory components arecoupled in common) so that, from the perspective of memory controller553, the two memory components appear to be a single component having adoubled storage capacity of either memory component 501A, 501B alone.

It should be noted that the various circuits disclosed herein may bedescribed using computer aided design tools and expressed (orrepresented), as data and/or instructions embodied in variouscomputer-readable media, in terms of their behavioral, registertransfer, logic component, transistor, layout geometries, and/or othercharacteristics. Formats of files and other objects in which suchcircuit expressions may be implemented include, but are not limited to,formats supporting behavioral languages such as C, Verilog, and VHDL,formats supporting register level description languages like RTL, andformats supporting geometry description languages such as GDSII, GDSIII,GDSIV, CIF, MEBES and any other suitable formats and languages.Computer-readable media in which such formatted data and/or instructionsmay be embodied include, but are not limited to, computer storage mediain various forms (e.g., optical, magnetic or semiconductor storagemedia, whether independently distributed in that manner, or stored “insitu” in an operating system).

When received within a computer system via one or more computer-readablemedia, such data and/or instruction-based expressions of the abovedescribed circuits may be processed by a processing entity (e.g., one ormore processors) within the computer system in conjunction withexecution of one or more other computer programs including, withoutlimitation, net-list generation programs, place and route programs andthe like, to generate a representation or image of a physicalmanifestation of such circuits. Such representation or image maythereafter be used in device fabrication, for example, by enablinggeneration of one or more masks that are used to form various componentsof the circuits in a device fabrication process.

In the foregoing description and in the accompanying drawings, specificterminology and drawing symbols have been set forth to provide athorough understanding of the present invention. In some instances, theterminology and symbols may imply specific details that are not requiredto practice the invention. For example, any of the specific numbers ofbits, signal path widths, signaling or operating frequencies, componentcircuits or devices and the like may be different from those describedabove in alternative embodiments. Additionally, links or otherinterconnection between integrated circuit devices or internal circuitelements or blocks may be shown as buses or as single signal lines. Eachof the buses may alternatively be a single signal line, and each of thesingle signal lines may alternatively be buses. Signals and signalinglinks, however shown or described, may be single-ended or differential.A signal driving circuit is said to “output” a signal to a signalreceiving circuit when the signal driving circuit asserts (or deasserts,if explicitly stated or indicated by context) the signal on a signalline coupled between the signal driving and signal receiving circuits.The term “coupled” is used herein to express a direct connection as wellas a connection through one or more intervening circuits or structures.Integrated circuit device “programming” may include, for example andwithout limitation, loading a control value into a register or otherstorage circuit within the device in response to a host instruction (andthus controlling an operational aspect of the device and/or establishinga device configuration) or through a one-time programming operation(e.g., blowing fuses within a configuration circuit during deviceproduction), and/or connecting one or more selected pins or othercontact structures of the device to reference voltage lines (alsoreferred to as strapping) to establish a particular device configurationor operation aspect of the device. The terms “exemplary” and“embodiment” are used to express an example, not a preference orrequirement.

While the invention has been described with reference to specificembodiments thereof, it will be evident that various modifications andchanges may be made thereto without departing from the broader spiritand scope. For example, features or aspects of any of the embodimentsmay be applied, at least where practicable, in combination with anyother of the embodiments or in place of counterpart features or aspectsthereof. Accordingly, the specification and drawings are to be regardedin an illustrative rather than a restrictive sense.

What is claimed is:
 1. An integrated circuit device comprising:signaling contacts to receive respective data signals from a sourceexternal to the integrated circuit device; storage elements to storedata values conveyed in the data signals; and multiplexing circuitscoupled between the signaling contacts and the storage elements, eachmultiplexing circuit having: a data signal output coupled to arespective one of the storage elements, a first data signal inputcoupled to a respective one of the signal contacts to receive acorresponding one of the data signals therefrom, a second data signalinput coupled to an output of at least one other of the multiplexingcircuits, a configuration signal input to receive a respectiveconfiguration signal, and transistor switching elements to switchablycouple either the first data signal input or the second data signalinput to the data signal output in accordance with a state of theconfiguration signal received at the configuration signal input; whereinthe signaling contacts constitute at least part of a variable-width datainterface of the integrated circuit device, the integrated circuitdevice further comprising programmable configuration circuitry to (i)store an interface width value that indicates how many of the signalingcontacts are to receive respective data signals during operation of theintegrated circuit device, and (ii) output the respective configurationsignals to the multiplexing circuits in accordance with the interfacewidth value.
 2. The integrated circuit device of claim 1 wherein thesignaling contacts comprise quantity N signaling contacts and themultiplexing circuits comprise at least quantity N−1 multiplexingcircuits.
 3. The integrated circuit device of claim 1 wherein theprogrammable configuration circuitry is capable of storing at least thefollowing interface width values: a first interface width valueindicating that all of the signaling contacts are to receive respectivedata signals during operation of the integrated circuit device; a secondinterface width value indicating that only half of the signalingcontacts are to receive respective data signals during operation of theintegrated circuit device; and a third interface width value indicatingthat only one-fourth of the signaling contacts are to receive respectivedata signals during operation of the integrated circuit device.
 4. Theintegrated device of claim 3 wherein, when the first interface widthvalue is stored within the programmable configuration circuitry, theprogrammable configuration circuitry outputs the respectiveconfiguration signals to the multiplexing circuits in respective statesto switchably couple, within each of the multiplexing circuits, thefirst data signal input to the data signal output.
 5. The integrateddevice of claim 3 wherein the signaling contacts comprise quantity Nsignaling contacts and, when the second interface width value is storedwithin the programmable configuration circuitry, the programmableconfiguration circuitry outputs the respective configuration signals tothe multiplexing circuits in respective states to switchably couple,within N/2 (N divided by two) of the multiplexing circuits, the seconddata signal input to the data signal output.
 6. The integrated circuitdevice of claim 5 wherein the multiplexing circuits comprise at leastquantity N−1 multiplexing circuits and, when the second interface widthvalue is stored within the programmable configuration circuitry, theprogrammable configuration circuitry outputs the respectiveconfiguration signals to the multiplexing circuits in respective statesto switchably couple, within at least (N/2)−1 of the multiplexingcircuits, the first data signal input to the data signal output.
 7. Theintegrated device of claim 3 wherein the signaling contacts comprisequantity N signaling contacts and, when the third interface width valueis stored within the programmable configuration circuitry, theprogrammable configuration circuitry outputs the respectiveconfiguration signals to the multiplexing circuits in respective statesto switchably couple, within 3*N/4 (three times N divided by four) ofthe multiplexing circuits, the second data signal input to the datasignal output.
 8. The integrated circuit device of claim 7 wherein themultiplexing circuits comprise at least quantity N−1 multiplexingcircuits and, when the third interface width value is stored within theprogrammable configuration circuitry, the programmable configurationcircuitry outputs the respective configuration signals to themultiplexing circuits in respective states to switchably couple, withinat least (N/4)−1 of the multiplexing circuits, the first data signalinput to the data signal output.
 9. The integrated circuit device ofclaim 1, wherein the signaling contacts comprise quantity N signalingcontacts and wherein, when the interface width value indicates that onlyone of the N signaling contacts is to receive respective data signalsduring operation of the integrated circuit device, the programmableconfiguration circuitry outputs the respective configuration signals tothe multiplexing circuits in respective states to switchably couple,within each of the multiplexing circuits, the second data signal inputto the data signal output.
 10. A method of operation within anintegrated circuit device having multiplexing circuits coupled betweensignaling contacts and storage elements, each multiplexing circuithaving a data signal output coupled to a respective one of the storageelements, a first data signal input coupled to a respective one of thesignaling contacts, and a second data signal input coupled to the datasignal output of a neighboring one of the multiplexing circuits, themethod comprising: storing, within a programmable mode register of theintegrated circuit device, an interface width value that indicates howmany of the signaling contacts are to receive respective data signalsduring operation of the integrated circuit device; and outputtingconfiguration signals to the multiplexing circuits in either a firststate or a second state in accordance with the interface width value;and within each of the multiplexing circuits, switchably coupling thedata signal output to either the first data signal input or the seconddata signal input according to whether a respective one of theconfiguration signals is in the first state or the second state,respectively.
 11. The method of claim 10 wherein the signaling contactscomprise quantity N signaling contacts and the multiplexing circuitscomprise at least quantity N−1 multiplexing circuits.
 12. The method ofclaim 10 wherein storing the interface width value within theprogrammable mode register comprises storing at least one of first,second or third interface width values, the first interface width valueindicating that all of the signaling contacts are to receive respectivedata signals during operation of the integrated circuit device, thesecond interface width value indicating that only half of the signalingcontacts are to receive respective data signals during operation of theintegrated circuit device, and the third interface width valueindicating that only one-fourth of the signaling contacts are to receiverespective data signals during operation of the integrated circuitdevice.
 13. The method of claim 12 wherein outputting configurationsignals to the multiplexing circuits in either the first state or thesecond state in accordance with the interface width value comprisesoutputting the configuration signals all in the first state when thefirst interface width value is stored within the programmable moderegister.
 14. The method of claim 13 wherein the signaling contactscomprise quantity N signaling contacts and wherein outputtingconfiguration signals to the multiplexing circuits in either the firststate or the second state in accordance with the interface width valuecomprises outputting N/2 (N divided by two) of the configuration signalsin the second state when the second interface width value is storedwithin the programmable mode register and outputting a remainder of theconfiguration signals in the first state.
 15. The method of claim 14wherein the multiplexing circuits comprise at least quantity N−1multiplexing circuits and wherein outputting the remainder of theconfiguration signals in the first state comprises outputting (N/2)−1 ofthe configuration signals in the first state when the second interfacewidth value is stored within the programmable mode register.
 16. Themethod of claim 12 wherein the signaling contacts comprise quantity Nsignaling contacts and outputting configuration signals to themultiplexing circuits in either the first state or the second state inaccordance with the interface width value comprises outputting 3*N/4(three times N divided by four) of the configuration signals in thesecond state when the third interface width value is stored within theprogrammable mode register and outputting a remainder of theconfiguration signals in the first state.
 17. The method of claim 16wherein the multiplexing circuits comprise at least quantity N−1multiplexing circuits and wherein outputting the remainder of theconfiguration signals in the first state comprises outputting (N/4)−1 ofthe configuration signals in the first state when the third interfacewidth value is stored within the programmable mode register.
 18. Themethod of claim 10 wherein outputting configuration signals to themultiplexing circuits in either the first state or the second state inaccordance with the interface width value comprises outputting all theconfiguration signals in the second state when the interface width valueindicates that only one of the signaling contacts is to receiverespective data signals during operation of the integrated circuitdevice.
 19. An integrated circuit device comprising: signaling contactsto receive respective data signals from a source external to theintegrated circuit device; storage elements to store data valuesconveyed in the data signals; multiplexing circuits coupled respectivelybetween the signaling contacts and the storage elements, eachmultiplexing circuit having: a data signal output coupled to arespective one of the storage elements, a first data signal inputcoupled to a respective one of the signal contacts to receive acorresponding one of the data signals therefrom, a second data signalinput coupled to an output of at least one other of the multiplexingcircuits, a configuration signal input to receive a respectiveconfiguration signal, and transistor switching elements to switchablycouple either the first data signal input or the second data signalinput to the data signal output according to whether the configurationsignal received at the configuration signal input is in a first state ora second state; a programmable mode register; means for storing, withinthe programmable mode register, an interface width value that indicateshow many of the signaling contacts are to receive respective datasignals during operation of the integrated circuit device; and means foroutputting respective configuration signals to the multiplexing circuitsin either the first state or the second state in accordance with theinterface width value.